Recent years have witnessed the proliferation of renewable power sources that use renewable energy such as solar energy to generate electric power. The electric power that is generated by a renewable power source can both be consumed by the consumer who has installed the renewable power source, and can also be supplied by way of a distribution line to a higher-order system such as a power transmission network. However, the amount of power generated by a renewable power source fluctuates due to, for example, the amount of solar radiation, and the electric power that is supplied to the higher-order system therefore fluctuates, thereby raising the problem of instability of the electric power that flows to the higher-order system.
As a technology for solving the above-described problem, technology has been proposed for stabilizing fluctuation in power flow at a higher-order system linking node at which a distribution line links with a higher-order system (such as a microgrid or an electric power substation that is under the control of an electric power distribution business). More specifically, a technology has been proposed for stabilizing fluctuation of power flow at a higher-order power system linking node by measuring the fluctuation of power flow at the higher-order power system linking node, and based on the measured value, regulating the amount of charging and discharging of a power storage device that is connected to the distribution line or by regulating the amount of power consumption of a controllable load that is connected to the distribution line (for example, refer to Patent Document 1).
In the above-described technology, the installation location at which a power storage device or controllable load is installed is limited by such factors as the availability of installation space and by the degree to which voltage on the distribution line is stable. As a result, a power storage device or controllable load may be installed at a location that is remote from the higher-order power system linking node. In such cases, the power storage device or controllable load will be installed at a location that is distant from the device that measures the fluctuation of power flow at the higher-order power system linking node, and the need will therefor arise for the long-distance transmission of the control signals for regulating the amount of charging/discharging of the power storage device or the amount of power consumption of the controllable load. Although the transmission distance of the control signals will vary with the size of the area in which the distribution line is installed, in general, the transmission distance will range in the order of from several hundred meters to several kilometers or more.
When control signals are transmitted over a long-distance, they will be prone to delays or interruptions. Delays or interruptions of the control signals will impede the accurate control of power flow fluctuation, and the reliability of the control of power flow fluctuation will therefore drop. The installation of a dedicated circuit for control signals may be considered as a means to limit the delay or interruption of control signals, but when the installation of power storage devices or controllable loads is distributed among individual consumers, the number of transmission destinations of the control signals may rise to the order of several thousand, and the installing dedicated circuits for all of these consumers will be problematic.
In response to these problems, Non-Patent Document 1 discloses a technology in which a power storage device or controllable load is combined with each renewable power source and the combined power storage devices or controllable loads are then used to control the fluctuation of electric power that is generated at the renewable power source for each individual renewable power source. In this technology, control of power flow fluctuation can be realized with a high level of reliability because power flow fluctuation can be controlled without requiring long-distance transmission of control signals.